Severe weather is expected in Missouri tonight, and now the National Weather Service is concerned storms could come together to form a derecho.

This graphic from the National Weather Service shows the potential threats from severe weather tonight.

A derecho is a long-lived, widespread, straight line wind storm. Such events have drawn national media attention including last week, when a derecho that swept across several midwestern states caused multiple tornadoes, heavy rain and widespread damage and has been blamed for five deaths and numerous injuries.

Meteorologist Mike July stresses that the formation of such a storm is possible and not definite. Whether a derecho forms or not, severe weather is likely, and he wants Missourians to be prepared.

“Continue to monitor your local media because storms haven’t formed yet, and once they begin to form we’ll kind of see how they evolve,” says July. “If they begin to show signs that we look for, then we’ll have to maybe ramp things up a little bit.”

If the system evolves as some computer models say it will, it could produce winds of 70 miles per hour or more.

“Right now we’re kind of thinking in excess of 75 miles an hour winds are certainly possible, and it’s highlighted from an area southeast of Nebraska all the way over to St. Louis, so it’s a fairly wide corridor,” says July.

The public can often be dismissive of straight-line winds as a threat, but a prolonged straight-line wind even can be as damaging or more so than a tornado.

“In a tornado, if you kind of think of it in real estate coverage, it’s a small area that it covers,” says July. “If you’re talking about a true derecho, it could very well be, from the north end to the south end, it could be 100 to 200 miles long, and along that entire length you’re getting damaging winds.”

There is also a threat of flash flooding.

“We’re talking about one to three inches of rain possibly, and even from a localized area, four inches of rain,” says July. “We have multiple hazards to be concerned about this evening.

For National Weather Service information for your area, visit these NWS pages.

The National Weather Service’s Storm Prediction Center is warning of a slight risk for severe weather for much of Missouri Thursday and a smaller portion of the state on Friday. Missourians are encouraged to watch for weather updates and be aware of changing conditions.

This graphic from the National Weather Service’s St. Louis Office shows where the Storm Prediction Center says there is a slight chance of severe weather Thursday and Friday.

The National Weather Service says storms could move into southwest Missouri after midnight Thursday morning and begin impacting northwest Missouri by around daybreak. Storms the morning carry some risk for severe weather, primarily from hail.

Meteorologist Steve Lindenberg says later Thursday storms could become stronger if enough instability is present.

“During the afternoon and evening we could get additional strong to severe weather with large hail and damaging winds the primary severe weather risk,” says Lindenberg. The Weather Service does not rule out the possibility of isolated tornadoes Thursday.

The front that will produce these storms is expected to move slowly and linger in the state Friday and into the weekend, presenting the possibility of more rounds of thunderstorms Friday and perhaps Saturday and Sunday. A slight chance for severe weather remains for Friday in most of the southern half of the state.

The Storm Prediction Center says the predictability of severe weather for Saturday and Sunday is too low to offer an outlook.

Forecasters are also concerned about the possibility of minor flooding in the next few days, but major, widespread flooding is not anticipated.

For National Weather Service information for your area, visit these NWS pages.

A tornado watch has been issued for 21 counties in southeast and south-central Missouri, for storms that have already prompted a tornado warning in Arkansas this morning. Those storms are anticipated to sweep northeast from southwestern Missouri through the St. Louis area.

These storms could produce large hail, damaging winds and tornadoes. Flooding is a possibility locally in southern Missouri, and more so in central and east-central Missouri where heavy rain has already fallen overnight.

Then for this afternoon will come storms that have caused the Storm Prediction Center in Oklahoma to say much of central and southern Missouri has a “moderate” risk for severe weather.

This graphic from the National Weather Service in Pleasant Hill illustrates the threats of severe weather today.

Today’s threat of tornadoes is the highest the state has been under so far this year, according to Meteorologist Jayson Gosselin with the National Weather Service in St. Louis.

“Unfortunately there will probably be at least one tornado in the state and there could be quite a few,” says Gosselin.

“It looks like it should warm up by this afternoon and get very unstable and a cold front will head from west to east across the state. Out ahead of that and along it we’re expecting thunderstorms that are going to be capable of very large hail, very strong winds as well as tornadoes possible.”

Storms are expected to form in Kansas and Oklahoma before sweeping through the state, first as discrete supercell thunderstorms, which Meteorologist Ryan Cardell with the Weather Service Office in Springfield says are generally the most dangerous.

“At that point the threat will switch over to being more of a straight-line wind threat with isolated tornadoes. That will happen early in the evening sometime.”

Flash flood warnings have already been issued in a swath of central and eastern Missouri where rainfall totals have ranged from between 2.5 to more than 3 inches from storms overnight. Gosselin says if more heavy rain does move through, more flash flooding issues are likely.

“Everything is very saturated now,” says Gosselin.

“This is a good time … before the storms have formed … to dust off your emergency plans,” says Cardell. “Make sure that’s all ready so that when the watches do come out you can kind of start heightening your situational awareness to where the storms currently are, if they’ve formed, things like that, so that way you’re kind of ready. When the tornado warning happens you’ve got one foot in place heading into your disaster plan.”

Missouri could experience severe weather several times in the next couple of days.

This graphic shows the chances for general or organized thunderstorms for Tuesday (left image), Wednesday (center image) and Thursday (right image) according to the Storm Prediction Center in Norman, Oklahoma.

The National Weather Service says storms today are expected to develop in southwest Missouri before pushing into central and northern Missouri in the afternoon and evening.

“We’re not expecting that to be severe,” says meteorologist Jenny Laflin at the Service’s Pleasant Hill office, “but as we go into the overnight hours we could see some additional development and some strengthening … and that’s where we’d look for severe potential, mainly between midnight and 8 a.m.”

Laflin says storms overnight should be widespread but only a few are likely to become severe, producing large hail. There is a lesser chance of damaging winds.

The greater chance of severe weather begins Wednesday.

“We have a warm front that’s lifting into the area and it’s just going to kind of park over central Missouri,” says Laflin. “We could see strong development across that boundary during the afternoon but our main window for severe weather is during the evening and early overnight hours, expecting large hail, damaging winds and potentially an isolated tornado or two.”

Laflin says the atmosphere Wednesday is predicted to be much like it was Thursday, when one thunderstorm in northwest Missouri produced three tornadoes that damaged several homes and outbuildings.

Meteorologist Ryan Cardell with the Weather Service’s Springfield Office says there will also be a chance of severe weather Thursday, and it will be more focused in the southern half of the state.

“That’s when the main upper-level dynamics are going to come through sweeping the main frontal boundary through the area from the west,” says Cardell. “That is probably going to be the better chance for any higher-end severe weather, like tornadoes.”

Cardell says heavy rainfall in localized areas could result in flooding as well, but severe weather is considered the primary threat.

The National Weather Service office in Kansas City has completed its assessments following yesterday’s storms. It believes one supercell thunderstorm spawned three separate tornado touchdowns along about a 35-mile path from around Weatherby to east of Spickard in northwest Missouri.

The first tornado touched down at about 3:03 p.m. about 3 miles east of Weatherby. It traveled more than 9 miles in about 12 minutes and left a damage path up to 200 yards wide. It produced EF-1 damage, meaning its winds are estimated to have reached up to 110 miles per hour.

The last of three tornadoes in northwest Missouri on Thursday, March 27 2014 touched down in Crowder State Park and passed north of Trenton. (photo from Facebook)

The second tornado was on the ground for less than three miles after it touched down at 3:22 p.m., north of Jameson. It caused EF-2 damage, with winds estimated at up to 130 miles per hour before lifting off the ground after 5 minutes.

The final tornado touched down in Crowder State Park northwest of Trenton at 3:55 p.m. and traveled more than 13 miles northeast to east of Spickard in 20 minutes. It left a damage path up to 500 yards wide and also produced EF-2 damage.

No injuries have been reported but homes, outbuildings and trees were damaged.

“We were really fortunate with this event,” says Warning Coordination Meteorologist Andy Bailey of the fact the storms caused no injuries despite the damage to homes and structures. “There were probably half a dozen to ten houses that were pretty heavily damaged along the path. I know of at least one mobile home that was completely destroyed.”

Bailey says it is possible other tornado touchdowns have gone unreported. Anyone who wants to report additional damage to the Weather Service for assessment can contact the local county emergency manager, or can reach the Weather Service on its Facebook page.

There is a slight risk that storms expected to pass through the state today will be severe, according to the National Weather Service.

This weather graphic courtesy of the National Weather Service office in Springfield.

Meteorologist Jared Leighton says a storm system moving in from the west is expected to spur thunderstorm development along a cold front. Storms are expected to develop in far eastern Kansas and move into western Missouri in the early to mid afternoon.

Leighton says the storms will move quickly through western and central Missouri.

“Storm motion will be straight to the east at perhaps up to 50, 60 miles per hour,” says Leighton. He predicts they will be in eastern Missouri and the St. Louis area around 7 or 8 p.m.

“We are expecting strong storms. They will be able to produce some hail, maybe even some winds,” says Leighton. “We’re not expecting any tornadoes. It’s not something we can rule out completely but definitely not something we’re expecting any kind of widespread activity on that.”

Leighton says southwest Missouri could see the strongest storms in the state.

“The strongest storms could form in southeast Kansas, east Kansas into far western Missouri. By the time the system actually gets into central and southeast Missouri it will probably be lined out into kind of a squall line. At that point your tornado threat is virtually nothing and your hail threat is very minimal as well. You’re basically a wind threat at that point,” says Leighton. “If you’re anywhere southeast of basically a Columbia to Springfield line you’re probably going to see a squall line … heavy rain, lighting, maybe some winds but that’s about it.”

The Attorney General’s Office says it has recovered more than $39,000 of money donated to help Joplin recover from the May, 2011 tornado, but used by a fundraiser for personal expenses.

Attorney General Chris Koster says Sidney Ray-Bazan agreed to pay $39,200 to the Community Foundation of the Ozarks for rebuilding efforts in Joplin. His office’s investigation revealed that she had taken a large portion of the $133,000 she collected as the owner of Relief Spark.

“The money was diverted by an unscrupulous fundraiser from donations intended to help tornado victims, but was instead diverted for her personal use,” says Koster.

The statewide tornado drill scheduled for tomorrow as part of Severe Weather Awareness Week has been postponed to Thursday.

The National Weather Service says the Federal Communications Commission has not granted a waiver to allow the test to proceed. Also many of the state’s local emergency management officials have told the Weather Service they cannot sound their sirens while temperatures are below freezing, as they are predicted to be tomorrow.

Severe weather is possible in parts of the Ozarks, the Bootheel and the St. Louis region this afternoon and evening.

This graphic from the National Weather Service office in Paducah, KY shows the expectation for severe weather in Southeast Missouri.

A cold front moving through the state is going to cause temperatures in central Missouri to drop from the 60s and 70s into the 40s. That same front has been causing hail and some strong wind gusts in north Missouri in the late morning and early afternoon.

That front has slowed slightly, and Meteorologist Jim Packett with the National Weather Service office in Paducah, Kentucky says as the afternoon progresses storms will form along and east of a line from St. Louis to west of Van Buren. There is a slight risk those storms will be severe. A moderate risk for severe weather exists south and east of Missouri.

The cold front is expected to be along that St. Louis to Van Buren-area line around 3:00 p.m., though Packett says variance could have that happen an hour earlier or an hour later.

The primary threat in areas of Missouri that might see severe weather is damaging wind. Packett says there is a slight tornado threat east of the St. Louis to Van Buren area line and a greater threat for tornadoes east of a line from Perryville to Poplar Bluff.

In Northwest Missouri some snowfall is possible, with accumulation estimates ranging from a trace of an inch to 2 inches north of a line from south of the Kansas City area to northeast Missouri to 2 to 4 inches north of a line from St. Joseph to south of Lamoni, Iowa.

There is also a flood risk in far northeast Missouri where prior snow melt is expected to combine with rainfall and could cause smaller creeks and streams to rise out of their banks.

Gusty winds are also possible with sustained winds expected from 20 to 30 miles per hour and gusts as high as about 50 miles per hour.

Storms tomorrow night and Thursday could bring some severe weather to Missouri.

This graphic from the National Weather Service in St. Louis illustrates part of the severe weather threat. Storms are also anticipated to produce up to around 2 inches of rain and hail in western Missouri before reaching eastern Missouri and the Bootheel.

National Weather Service Meteorologist Mark Britt says storms could begin tomorrow night in western Missouri.

He says storms Wednesday night will be isolated, “that could produce some hail over parts of western and central Missouri. Then as we go into Thursday, parts of eastern and southeastern Missouri could see a few severe thunderstorms.”

Britt says storms could intensify into Thursday morning, with, “possible isolated tornadoes … but the main threat at least right now looks like some damaging winds.”